Guitar Hero: Metallica - Cheat mode

Line 6 effects:
Press Green, Red, Yellow, Blue, Red, Yellow, Blue, Green. This unlocks additional Line 6 effects in the Music Studio.

Metallica Costumes:
Press Green, Red, Yellow, Blue, Blue, Yellow, Red, Green.

Hyperguitar, Hyperbass, and Hyperdrums:
Press Green, Blue, Red, Yellow, Yellow, Red, Green, Green.

Performance mode:
Press Yellow, Yellow, Blue, Red, Blue, Green.

Invisible Rocker:
Press Green, Red, Yellow, Yellow, Blue, Blue, Green.

Air instruments:
Press Red, Red, Blue, Yellow, Green, Green, Green, Yellow.

Always Slide:
Press Green, Green, Red, Red, Yellow, Red, Yellow, Blue. This turns all guitar notes (not chords) into touch pad sliding notes connected by purple lines. It has no effect online.

Auto Kick:
Press Yellow, Green, Red, Blue, Blue, Blue, Blue, Red. This mode automatically plays the bass pedal for the drummer. It has no effect online.

Always Drum Fill:
Press Red, Red, Red, Blue, Blue, Green, Green, Yellow.

Gem Color:
Press Blue, Red, Red, Green, Red, Green, Red, Yellow.

Flame Color:
Press Green, Red, Green, Blue, Red, Red, Yellow, Blue.

Star Color:
Press Red, Red, Yellow, Red, Blue, Red, Red, Blue.

Vocal Fireball:
Press Red, Green, Green, Yellow, Blue, Green, Yellow, Green.

Black Highway:
Press Yellow, Red, Green, Red, Green, Red, Red, Blue.

Unlock James Hetfield:
Earn 100 stars in vocalist career

Unlock King Diamond:
Beat the song Evil in any instrument career

Unlock Kirk Hammett:
Earn 100 stars in guitar career

Unlock Lars Ulrich:
Earn 100 stars in drum career

Unlock Lemmy:
Beat the song Ace of Spades in any instrument career mode

Unlock Robert Trujillo:
Earn 100 stars in bass career